Electronic transfer of healthcare record information between heterogeneous systems raises the need for healthcare information standards. Such standards improve the level of quality that healthcare organizations offer and also control the expenditure on healthcare services provided by these organizations. There are a large number of healthcare related applications that effectively support specific needs but are isolated or incompatible. There is an urgent need to integrate those applications or to interoperate between them, ensuring security concepts. The cost is another crucial aspect that should be considered in the integration of already implemented systems and the design of new systems. This paper aims to give a description of the current developed standards that can be used to provide interoperability in healthcare information systems and to make a short comparison between these standards, including the following: HL7, HL7’s CCOW, CEN/TC251 Healthcare Information System Architecture Standard. This paper also discusses a solution that is being developed in the Citizen Health System (CHS) project to achieve integration of data using a healthcare informatics standard. A test scenario to make some of the project’s modules visually interoperate is also implemented.